"so large as" is a correct and usable phrase in written English.
You can use it when comparing two things or indicating the size of something. For example, "The ballroom was so large as to fit 200 people."
Figures soon become so large as to be incomprehensible.
"Error ranges are so large as to be inconclusive," said Ken Zino, a Ford spokesman.
The list of offenders is so large as to be almost useless.
But the Fed's advantage in this case is not so large as with predicting inflation.
On the Texan side nothing looms so large as the egos.
How can you preserve competition with one party so large as a result?
Court judgments have been issued for sums so large as to require a lifetime to pay.
New York as I knew it was not so large as it is now.
But never before has infrastructure spending been so large as a share of world GDP.
Though that range was so large as to be of limited value, alarms went off in the birding world.
Often, the banned areas are so large as to effectively prohibit a sex offender from living anywhere in town.
